INTRODUCTION 5 



the useful metabolic products, such as alcohols, organic acids, and anti- 

 biotics, and the harmful products (toxins) are discussed at some length. 



Certain fungi cause diseases of plants and animals. The action of 

 fimgicides used to control these pathogens will be discussed from a theo- 

 retical viewpoint, since there is an enormous amount of literature dealing 

 with the practical application of fungicides. Too little attention has 

 been devoted to the mechanism of fungicidal action. 



The production of spores, which is of fundamental importance to the 

 fungus in the perpetuation of the species, affords many interesting prob- 

 lems in fungus physiology. Environmental and nutritional factors play 

 important roles in determining whether a fungus will spoiiilate under a 

 given set of conditions. These factors are discussed in some detail. 



The latter portion of the text emphasizes the activities of fungi in 

 nature. These topics include the discharge, dissemination, and germina- 

 tion of spores and the physiological aspects of parasitism, variation, and 

 inheritance. The physiology of parasitism and resistance is of special 

 interest to plant pathologists and medical mycologists. Most of the 

 examples are taken from the field of plant pathology. Perhaps the dis- 

 cussion of these problems will stimulate the interest and curiosity of the 

 student. A better understanding of parasitism will surely lead to a wiser 

 choice of control methods for certain fungi. 



No study of fungus physiology is complete without experimental work 

 in the laboratory. The judgment necessary to evaluate one's own work 

 is founded upon experience. Suggested laboratory exercises and demon- 

 strations, with brief instructions, are given at the end of the text. These 

 are selected to illustrate important principles, many of which can be 

 illustrated clearly only by direct observation of the varied reactions of 

 fungi to their environment. 



HISTORICAL DEVELOPMENT 



The development of fungus physiology is far from complete. While 

 some of the main outlines are clearly visible, much remains to be done. 

 Although space and time do not permit a complete review of the history 

 of this science, it is important to realize that its development was the 

 work of many minds and hands. The influence of the early investigators 

 continues, not only in their published work but also in the students they 

 trained. 



Some of the outstanding leaders in the development of fungus physi- 

 ology are Avorthy of special mention. Their names and their contribu- 

 tions are encountered frequently bj'" all students of this subject. Brief 

 mention of some of these men and their fields of interest and investigation 

 is made below. 



